In recent years, an apparatus which transmits power in a non-contact manner has been increasingly widespread. The power transmission apparatus includes a power transmission device which transmits power and a power reception device which receives the transmitted power. In addition, the power reception device includes a load such as a charging unit of a secondary battery.
The power transmission apparatus transmits power from the power transmission device to the power reception device using an electromagnetic induction method, a magnetic field resonance method, an electric field resonance method, or the like. In a power transmission apparatus using the electromagnetic induction method, the power transmission device and the power reception device are required to be close to each other in a transmittable region, and, on the other hand, in a power transmission apparatus using the magnetic field resonance method, the power reception device is installed in a transmittable region within several cm or several tens of cm from the power transmission device, and power can be transmitted.
Here, if the power reception device is out of a transmittable region where power of the power transmission device can be transmitted, that is, if the power transmission device transmits power in a state where power transmission efficiency is low, power which is not received is radiated into the space and thus has a harmful effect on human bodies or peripheral electronic apparatuses. In addition, power which is not transmitted is converted into heat, and thereby the power transmission device may emit heat or may catch fire in the worst case scenario.
In relation thereto, there is a technique in which the power transmission device and the power reception device are respectively provided with communication units, a power reception state is fed back from the power reception device to the power transmission device, the power transmission device transmits power if it is determined that the power reception device is set in the power transmission device, and the power transmission device stops transmitting power if the power reception device is released from the power transmission device.
However, in this technique, since a power transmittable state is determined merely based on the fact that the power reception device is set by communication, if the power reception device is separated from the power transmission device in a range where the power reception device is set in the power transmission device, particularly, if the power reception device is poorly set, radiation of power and heat emission due to a reduction in transmission efficiency cannot be prevented.